1. Field of the Invention
This invention relates to cutting tubes and more particularly relates to a tube cutting machine and method for improved cutting of tubes including tubes having bent portions.
2. Description of the Related Art
There are a variety of devices used for cutting tubes including manual pipe cutting tools, and saws that are conventionally used for cutting pipes and other tubular materials. For automated processes in factory settings, tube cutting machines or large power saws are often utilized. Fixtures may be used to hold tubes having bends in place while these tubes are cut by a band saw, for example. This process is messy and time consuming. Cutting tubes with saws in this manner also requires additional steps of deburring and/or cleaning to remove burrs that are inherent with the sawing process and to remove lubricant that is used to aid the cutting process.
Cleaner and more efficient machines such as those shown and described in U.S. Pat. Nos. 4,563,927 and 4,694,718 issued to Kinsley and assigned to Vogel Tool & Die Corporation (Vogel) implement a shearing process. The Vogel machine moves each of a scarf blade and a clamp by a cam mechanism that is actuated by a driving mechanism that also moves the cut-off blade. As such, the clamping movement and scarf cutting, both of which are effected in a horizontal direction, have a very limited range, as can be noted in the figures and as described in the Abstract of the Vogel patents. The range of motion for one of the clamps relative to the other is approximately an eighth to a quarter of an inch. Thus, in order to place a tube in the jaws for cutting, the tube must be inserted in a direction of the tube's axis through the opening between the jaws when the jaws have been opened the slight amount. Then the jaws are clamped on the tube in preparation for cutting. Therefore, the Vogel machines are not as versatile in handling tubes having other than straight configurations, and saws with Fixtures are typically used for cutting tubes that have bends. In either case additional steps may be needed to clean and/or deburr or otherwise finish a tube end.
The step of scarf cutting in the Vogel devices is for the purpose of thinning the tube so that the subsequent cut-off step does not deform the tube when punching through the thinned, scarffed portion. As may be appreciated, the shearing action of the Vogel devices during cut-off is a very energetic operation that will dent many of the materials being cut unless they are first thinned by a scarfing step. Relatedly, the Vogel machines are much faster than saws for cutting tubes, and the shearing operation does not leave chips of material as do saws. However, the Vogel machines often produce a double layer of slug material by squishing an upper portion of the material (near the thinned portion of the tube) against a lower portion of the material (a lower portion of the tube). This squishing of two layers together in which the lower layer is forced through by the upper layer and the cut-off blade during cut-off causes an untidy cut that must often be corrected by subsequent steps before the cut pieces can be shipped.